Or even better say in the description that all Pc-Engines are rgb capable, and you have a rare/special cable that lets you take advantage of it.
To be honest I've been thinking of just that, put all the components in the damn cable and that way I can say yep, all the components are in the cable, that it's "only" an amp, stick the comparison pic "amplified RGB vs unamplified RGB" in the listing, get rid of the "RGB vs AV" one and as for all the components being in the cable? That's there for any buyers who might want to whine after fact if they're not. You don't mod a console if you put all the amp circuitry in the cable, right? It's just like the Megadrive with its resistors, and the SNES with its capacitors, they need the signal altered, every console has this!
Of course, they do output RGB as standard! Through the socket, of course they do. It's just not amplified! We all know that, right?
Not doing it on my main account though, too risky. Other seller might point it out, claiming it's the "same mod as before," highlighting my older listing, etc. This account is done for for listing consoles for some significant time. I need this guy right off my back, with no recourse to screw with me. Every claim he's making to ebay might be bullshit but ebay aren't savvy with any of this subject.
Also reporting this guy's listings is a surefire way to get a blanket ban put on all Famicoms and PC Engines, as eBay realise they are too "in the dark" to differentiate between modded/unmodded.
Btw ebay forum goers are likely reading this topic.